help me to install and run version 2.9 in Ubuntu
You have to make a file executable before running it.I will explain two ways to do that here.
Gui way

Right click on blender
click on properties
click on permissions tab
check make as executable box

now apply your changes and run blender

command line way

navigate to the location were you have extracted blender via a file manager.

right click on empty space and select open terminal here.Note open terminal option may be in different sub menu for you.




now execute the following commands one by one

  chmod +x blender
  ./blender